En dash - it's surrounded by spaces. And I don't think the reddit engine tells you how to code it. A hyphen is the accepted substitute (for the en dash - two hyphens for an em dash).
An en dash is defined by its width, not the spacing around it. In fact, spacing around an em dash is permitted in some style guides. On the internet, though, the hyphen has generally taken over from the em dash (an en dash should not be used in that context).
Now, two hyphens—that's a recipe for disaster if I've ever heard one.
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